JPH1020476A - Reticle, method for utilizing photolithography, patterning method and formation of photoresist profile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilevel reticle to allow the transmission of a plurality of incident light intensity and a production of a multilevel of photoresist. SOLUTION: A process for producing the multilevel reticle to allow the transmission of a plurality of the incident light intensity is provided. A plurality of such incident light intensity are used for forming plural thicknesses in the photoresist profile. An imperfect transmissible film 54 used as one layer among the layers of the reticle is capable of providing intermediate intensity light. The intermediate intensity light has the nearly intermediate intensity between the non-attenuated intensity of the light passing a reticle substrate layer and the intensity of the completely attenuated light shut off by the opaque layer of the reticle. The exposed photoresist receives the light of two sets of the intensity, by which via holes are formed in the resist in response with the light of the higher intensity. The connection lines to the via are formed at the intermediate level of the photoresist in response with the intermediate light intensity. The method for forming the multilevel resist from the multilevel reticle and the multilevel reticle device are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates generally to integrated circuit processing and integrated circuit manufacturing. More specifically,
The present invention relates to a method for manufacturing a multi-level reticle and a multi-level photoresist pattern.

[0002]

2. Description of the Related Art The need for smaller, more powerful electronic products requires smaller structures of integrated circuits (ICs) and larger substrates. This also requires higher density packaging of circuits on IC substrates. The desire for smaller structured IC circuits requires that the interconnection between components and dielectric layers be as small as possible. Accordingly, research continues into reducing the width of via interconnects and connecting lines. In attempting to reduce the size of lines and vias in electrical circuits, it is natural to choose copper instead of aluminum. Copper has about twice the conductivity of aluminum and more than three times that of tungsten. As a result, the same amount of current can be delivered by a copper wire that is about half as wide as an aluminum wire.

[0003] Copper electromigration is much better than aluminum. For electromigration, copper is about 10 times better than aluminum. As a result, the copper wire can maintain electrical and mechanical integration even though it has a much smaller cross section than the aluminum wire.

However, there have been problems associated with the use of copper in IC processing. Care must be taken not to move the copper, as it contaminates many of the materials used in IC processing. In addition, copper is particularly susceptible to oxidation during the oxygen etching process. Care must be taken to ensure that the copper is not exposed to oxygen during etching, annealing, and processing that requires high temperatures. Also, copper oxide is difficult to remove. Further, when the structure is small, copper cannot be deposited on the substrate using a conventional aluminum deposition process. That is, new deposition processes are developed for use with copper instead of aluminum in IC interlevel dielectric lines and interconnects.

Due to the low gap filling capability, it is impractical to sputter metal, whether aluminum or copper, to fill small diameter vias. Chemical vapor deposition (CVD) to deposit copper
Technology is being developed in the industry. However, CV
Even with D technology, conventional etching processes cannot be used. The low volatility of the copper etch products requires that copper be removed (vaporized) at temperatures as high as about 250 ° C. This temperature is too high for a photoresist mask. Since wet etching is isotropic, it is too inaccurate for many applications. Therefore, I
The C processing industry has evolved a process of forming vias using CVD without etching copper. The new method is called an inlay process or a damascene process.

A damascene method for forming vias or interconnects between a substrate surface and an overlying dielectric surface is described below. First, a substrate serving as a base is completely covered with a dielectric such as an oxide. Then, a patterned photoresist profile is formed over the oxide. The resist profile has openings or holes formed in the photoresist at locations corresponding to regions of the oxide where vias are to be formed. Other areas of the oxide that are left as is are covered with photoresist. The photoresist covered dielectric is then etched to remove oxides located under the holes formed in the photoresist. Thereafter, the photoresist is stripped. Thereafter, the via is filled with copper (CVD copper) by a CVD method. Thus, a layer consisting of an oxide and a copper via penetrating it is formed on the substrate surface. The remaining excess copper is removed using a chemical mechanical polish (CMP) process as is known in the art.

As the damascene process is relatively new to the IC industry, the technology is being improved. One improvement is the dual damascene method. In the dual damascene method, vias, interconnections, and lines are formed in the dielectric at two different levels. Given the above damascene process example, the dual damascene method involves depositing from a new (oxide) surface to a level in the oxide between the underlying substrate surface and the new (oxide) surface. Oxide in the second
, Ie, connection lines are added. The dual damascene method is described in more detail in FIGS. 1-6 as prior art in co-pending application Ser. No. 08 / 665,014, filed Jun. 10, 1996. This co-pending application is a co-pending application entitled “Method for Transferring a Multi-Level Photoresist Pattern”.
level Photoresist Pattern), inventor Tue Nguyen, S
hengTeng Hsu, Jer-shen Maa and Bruce Dale Ulric
h, the agent case reference number SMT162, which is assigned to the same assignee as the present invention.

One known method of performing a dual damascene process relies on a plurality of photoresist masks and etching steps. A single level photoresist profile is formed on the deposited dielectric, and a via pattern is formed by etching to a first interlevel in the dielectric material. At this point in the process, the via has been only partially etched. The photoresist is then stripped and a second single-layer photoresist profile is formed on the dielectric surface, thereby forming an interconnection pattern up to a second interconnect level in the dielectric material. The interconnect is formed by etching. Simultaneously with the etching of the interconnection, the via is etched such that the interconnection in the underlying substrate layer is exposed to allow electrical connection.

Another known method of performing a dual damascene process is to form vias and interconnections at multiple levels in an IC dielectric using multiple levels, ie, photoresist profiles having multiple thicknesses. It is. Electron beams or lasers are used to write multilevel patterns directly on photoresist, but are not practical from a commercial perspective. The so-called "gray-tone" mask, consisting of a repeating pattern of points that appear as transparent holes on the reticle chrome mask, is called Pierre Sixt "Phase Masks and Gray-Tone Masks", Semicon
It has also been used to form multi-level resist profiles, as described in ductor FabTech, 1995, page 209. Sixt also outlines a process for transferring a multilevel resist onto a dielectric. The process relies on one-to-one etch selectivity between the dielectric material and the resist material. The dielectric and the overlying photoresist profile are then etched together so that any exposed dielectric material is etched at the same rate as the overlying photoresist material. As the layer of resist becomes thinner, the depth of etching into the dielectric increases. As a result, the shape of the dielectric after etching generally resembles the photoresist pattern located on the dielectric at the beginning of the process.

The use of a multi-level reticle for the phase shift of light in the manufacture of a photoresist mask involves:
Known in the art. These multi-level reticles, ie, phase shift reticles, are used to reduce constructive unintended interference of light patterns diffracting from the reticle aperture. Constructive interference is in-phase interference of light from two different light sources. Irradiation of the aperture with light causes at least some diffraction, even if the light is highly coherent. The pattern of light diffracted through the aperture depends on the shape of the aperture and the wavelength of the light, as is known in the art.

As noted above, phase shift reticles have been developed to minimize the problem of in-phase optical interference effects. The general principle of a phase shift reticle is to change the phase of the light to promote positive and negative phase interference in the area of the photoresist mask that irradiates the plurality of diffraction sources. That is, light from one diffraction source is
Are adjusted to have a phase difference of 180 degrees from the two diffraction sources, so that the diffraction effects from the two diffraction sources are self-cancelling.

A typical method of performing this 180 degree phase shift is to use a so-called "halftone" film, ie, a partially permeable film. A typical phase shift reticle having a halftone film is disclosed in Garofalo et al., US Pat. No. 5,358,827. Another phase-shifting multi-level reticle is "The Control of Sidelobe Intensity of the Chrome Pattern (COSAC) in Halftone Phase Shift Masks.
Chrome Pattern (COSAC) in Half-Tone Phaseshifting
Mask) ", 1995 International Conference on Solid
State Devices and Materials, August 21-24, 1995, 935-937, Kobayashi, Oka, Watanab
e, Inoue and Sakiyama. Another document describing a similar phase shift reticle is Le
"Improving Resolution in Photolithography wit," by venson, Viswanathan and Simpson.
ha Phase shifting Mask) ”, IEEE Transactions on
Electron Devices, Vol. ED-29, No. 12, December 1982.

The above disclosure shows a reticle consisting of a transparent substrate made of a quartz material that transmits substantially all of the illuminating light. The reticle is a halftone film covering the substrate to shift the phase of the transmitted light, that is, a phase difference film (phase difference film).
shifting film). An opaque film for substantially blocking transmitted light covers the halftone layer. Through the use of phase shifts that cause positive and negative phase interference, these reticles produce light of substantially two intensities, 100% intensity and 0% intensity,
This forms a single level photoresist mask, as is known in the art. Alternatively, it can be said that the reticle generates light at a single intensity (100% transmission) or blocks light (0% transmission). The phase shift performed using a single level photoresist mask is performed to more clearly define features such as vias and to reduce the effects of diffraction.

[0014]

One problem with dual damascene processes involving multiple photoresist masks and etching steps is photoresist profile alignment. If the two photoresist profiles are not correctly aligned, misalignment will occur at the intersection shape in the dielectric material. That is, the conductive lines associated with the first photoresist pattern cannot intersect exactly with the vias associated with the second photoresist profile. Alignment errors can be corrected by oversizing the crossing shape, but reduce the overall effect of reducing the size of the connection lines and vias. Alignment issues reduce yield, increase IC processing costs, and increase IC processing complexity.

One problem with a method of performing a dual damascene process of forming vias and interconnections in an IC dielectric using multiple levels, ie, photoresist profiles having multiple thicknesses, is: , A dielectric material and a photoresist material having the same etch selectivity. Also, it is difficult to transfer various shapes, especially small or relatively complex shapes, to a dielectric using this method. Polymers and by-products of the etching process tend to collect in areas of the resist pattern, which changes the shape of the resist profile and the etch rate. In addition, the literature states that the resolution produced by the pixel size in the gray-tone mask is limited so that vias produced by this method are about 25 μm.
And has a relatively large size. Vias of this size are about two orders of magnitude larger than vias formed by conventional methods and are not suitable for most IC processing.

A conventional reticle, ie, a two-level reticle, comprises a transparent substrate that transmits substantially all of the illuminating light and an opaque substrate that does not substantially transmit illuminating light. Light transmitted through a square aperture two-level reticle forms a general aperture shape, and some diffraction of the light occurs around the edges of the aperture shape. One common problem associated with in-phase light interference effects arises in the region between two vias formed on a photoresist mask from light passing through two corresponding aperture holes in the reticle. In-phase light interference effects of light passing through the two via apertures often occur between the two vias, resulting in unintended regions of thin resist that eventually result in defects in the IC substrate etched from the photoresist. This process is described in further detail in FIGS. 1 and 2 of the embodiment.

Typically, conventional halftone materials are:
It is selected for a phase shift characteristic that is completely different from the optical attenuation characteristic. Accordingly, the halftone film of the phase shift reticle is selected to impart a 180 degree phase shift to the transmitted light with substantially no attenuation, as disclosed in the Levenson reference. Alternatively, the halftone film is
As disclosed in Kobayashi et al., It is selected to provide a 180 degree phase shift to the transmitted light while substantially attenuating the intensity of the transmitted light.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a multilevel reticle that transmits a plurality of incident light intensities and a method of manufacturing a multilevel photoresist. It is.

[0019]

The reticle of the present invention comprises:
A reticle through which incident light passes to define a predetermined illuminated area on the photosensitive photoresist surface, the first transmission level film generating a first intensity of transmitted light;
A second intensity that generates transmitted light of a second intensity greater than the intensity of
And a third transmission level film that generates transmitted light having a third intensity greater than the second intensity.
Thereby, the above object is achieved.

According to a preferred embodiment, the third
Is a substrate, the second transmission level film is located on the third transmission level substrate, and the first transmission level film is located on the second transmission level film.

Further, according to a preferred embodiment, the first
Is an opaque film selected from the group consisting of Cr, CrO and iron oxide, whereby the first transmission level film substantially blocks incident light.

According to a preferred embodiment of the present invention, the third
Is selected from the group consisting of quartz, synthetic quartz, and glass, whereby the third transmission level film is transparent to pass substantially all incident light.

According to a preferred embodiment of the present invention, the second
The first transmission level film has a first transmission level opening penetrating through the first transmission level film so as to expose a predetermined region of the third transmission level film; The second transmission level region has a second transmission level opening penetrating the second transmission level film so as to expose a predetermined region.

According to a preferred embodiment, the second
The phase difference between the reticle transmission level films is transmitted such that the transmission level film of the reticle retards the phase of light by a predetermined amount, thereby reducing in-phase light interference effects at the adjacent illuminated boundaries of the photoresist. Improve light intensity resolution.

Further, according to a preferred embodiment, the second
Of the transmitted light retards the phase of the transmitted light by about 90 °.

According to a preferred embodiment, a plurality of second transmission level films are provided, and each of the plurality of second transmission level films is greater than the first intensity. The transmitted light is generated at one of a plurality of second intensities smaller than the second intensity, thereby providing light in the second intensity range.

Further, according to a preferred embodiment, the first
Is composed of a plurality of second transmission level films, each of the plurality of second transmission level films is an incompletely permeable film layer, and the light transmission characteristic of the first transmission level film is As occurs, the intensity characteristics of the light transmitted through the plurality of second transmission level films are cumulative.

According to a preferred embodiment, the first
Wherein said permeation level membrane comprises a first number of said partially permeable membrane layers that is substantially all of said plurality of partially permeable membrane layers;
The second transmission level membrane includes a second number of the partially permeable membrane layers that is less than the first number.

Further, according to a preferred embodiment, the second
Is selected from the group consisting of indium tin oxide and molybdenum oxynitride, whereby the second transmission level film attenuates the transmitted light intensity by a predetermined percentage.

Further, according to a preferred embodiment, the second
The transmission level film transmits between about 10% and less than about 90% of the incident light, whereby the attenuation characteristics of the second transmission level film include the first transmission level film attenuation characteristic and the third transmission level film. About halfway between the level film attenuation characteristics and when light is directed to the photosensitive surface, the reticle forms at least three distinct intensities on the illuminated area of the photoresist.

The method of using photolithography according to the present invention is a method of using photolithography for forming a reticle, which transmits incident light, on a reticle substrate.
a) depositing at least one partially permeable membrane over the reticle substrate, the partially permeable membrane partially transmitting incident light, wherein the partially permeable membrane transmits through the partially permeable membrane; Reduce the light intensity by a predetermined percentage at
Said reticle substrate passing substantially all light incident on said reticle substrate; and b) depositing an opaque film over said reticle substrate, said opaque film blocking light. Wherein substantially all incident light is attenuated, and c) selective portions of the opaque film deposited in step b) and the partially permeable film deposited in step a) Is etched to expose predetermined regions of the reticle substrate and the partially permeable film, whereby light guided to the reticle is exposed to the predetermined regions of the reticle substrate, the partially permeable film and the remaining opaque film. Generating at least three light intensities transmitted through the light source, thereby achieving the above object.

According to another aspect of the present invention, a method of using photolithography according to the present invention is a method of using photolithography in which a reticle for transmitting incident light is formed on a reticle substrate, wherein the transmitted light is photosensitive. Illuminating regions of the surface, each of the regions being illuminated with a predetermined level of transmitted light, the method comprising: a) covering the reticle substrate;
Depositing at least one partially permeable membrane partially transmitting incident light, said partially permeable membrane reducing light intensity by a predetermined percentage in transmission through said partially permeable membrane; The reticle substrate transmitting substantially all light incident on the reticle substrate; and b) depositing an opaque film over the reticle substrate, wherein the opaque film blocks light. Wherein substantially all incident light is attenuated; and
c) etching the opaque film deposited in step b) and selective portions of the partially permeable film deposited in step a) to define predetermined areas of the reticle substrate and the partially permeable film; And the light guided to the reticle is transmitted through the reticle substrate, the partially permeable film and the predetermined region of the remaining opaque film to have at least two thicknesses on the photosensitive surface. Generating a patterned profile, thereby achieving said objective.

According to a preferred embodiment, said step a) comprises the step of applying a plurality of imperfectly permeable membranes to successive layers, wherein the light transmission properties of each of said imperfectly permeable membranes are The incident light that accumulates and passes through the imperfectly permeable film is gradually attenuated, the plurality of imperfectly permeable films having different etch selectivities, and adjacent imperfectly permeable films being etched differently. Need a chilling process,
Step c) comprises etching a selective portion of the predetermined imperfectly permeable membrane to expose an underlying imperfectly permeable membrane layer, thereby combining a plurality of the imperfectly permeable membranes. Comprises providing a plurality of transmitted light intensities.

According to a preferred embodiment, the opaque film is selected from the group consisting of Cr, CrO and iron oxide.

According to a preferred embodiment, the partially permeable film is selected from the group consisting of indium tin oxide and molybdenum oxynitride.

According to a preferred embodiment, the reticle substrate is selected from the group consisting of quartz, synthetic quartz, and glass.

[0037] Also according to a preferred embodiment, the partially permeable film transmits about 10% to less than about 90% of the incident light, thereby reducing the attenuation characteristics of the partially permeable film. , Substantially between the reticle substrate attenuation characteristic and the opaque film attenuation characteristic.

Also, according to a preferred embodiment, said step a) is performed such that the cumulative attenuation of said plurality of imperfectly permeable films substantially duplicates the light transmission characteristics of said opaque film. Step b) includes the step a) because the step of depositing a permeable membrane substantially blocks the transmission of light.

According to a preferred embodiment, the imperfectly transmitting film delays the phase of the incident light by a predetermined degree, so that the phase difference introduced in the transmission through the imperfectly transmitting film decreases the transmitted light intensity. Improve resolution to reduce in-phase light interference effects in illumination of photosensitive surfaces.

According to a preferred embodiment, the step a) includes a step of adhering the imperfectly permeable film to a layer adjacent to the reticle substrate and located on the reticle substrate. Wherein said step b) comprises attaching said opaque membrane to a layer adjacent to and overlying said partially permeable membrane, said step c) comprising: Etching a selected portion of the opaque film such that light is introduced into the partially permeable film without transmitting light through the opaque film, wherein step c) comprises: Etching selected portions of the imperfectly permeable film and the opaque film such that light is directed to selected portions of the reticle substrate without transmitting light through the film and the partially permeable film; Include the steps to Whereby light having at least three intensity illuminates the photosensitive surface.

According to a preferred embodiment, the step c) comprises the step of: i) forming a first pattern on the opaque film of the photoresist having a first pattern including an opening penetrating the first layer. And ii) etching a predetermined area of the opaque film exposed through the opening provided in the photoresist pattern formed in the step i) to form the opaque film. Exposing a first region of the partially permeable membrane underlying the reticle and etching the first region of the partially permeable membrane to expose the reticle under the partially permeable membrane Exposing a predetermined area of the substrate; and iii) forming a second layer of photoresist over the opaque film, the second layer having a second pattern having an opening through the second layer. , I
v) etching a predetermined area of the opaque film exposed through the opening in the second pattern of the photoresist formed in the step iii) to remove the second region of the imperfectly permeable film; And the light introduced into the predetermined area of the reticle substrate is transmitted at a first intensity, and the light introduced into the second area of the imperfectly permeable film is exposed to the imperfections. The light transmitted through the permeable film and the substrate located thereunder at a second intensity is transmitted to the remaining opaque film by the opaque film, the imperfectly permeable film located therebelow, and the substrate. Transmit at an intensity of 3 so that the photosensitive surface is illuminated.

Further, according to a preferred embodiment, the incident light guided to the reticle has a predetermined wavelength and a predetermined intensity.

The reticle of the present invention is a reticle for transmitting incident light to form a profile pattern having a plurality of thicknesses on a photosensitive surface, wherein the reticle attenuates a predetermined percentage of the incident light to a first thickness. Transparent film forming a photoresist region having a thickness, and an opaque film blocking substantially all incident light to form a photoresist region having a second thickness greater than the first thickness. And a transparent substrate that transmits substantially all of the incident light to form a photoresist region having a third thickness less than the first thickness, thereby achieving the above object. .

According to a preferred embodiment, the third
An opening having a thickness of substantially zero is formed in the photoresist film.

According to another aspect of the present invention, a reticle of the present invention is a reticle for transmitting incident light to form a profile pattern having a plurality of thicknesses on a photosensitive photoresist surface, wherein the reticle comprises: Forming a transparent substrate that allows substantially all incident light to pass therethrough to form an opening in the photoresist film, and that blocks substantially all incident light to form a photoresist region having a second thickness. An opaque film, wherein the reticle comprises a partially permeable film that attenuates a predetermined percentage of the incident light, thereby forming a photoresist region having a first thickness. The height is about 1/3 of the second thickness, thereby achieving the above object.

A method of forming a photoresist pattern according to the present invention is a method of forming a photoresist pattern having a predetermined profile formed by exposing a predetermined pattern of light transmitted through a reticle formed over a reticle substrate. Wherein the method comprises the steps of: a) depositing one or more films that imperfectly transmit incident light over the reticle substrate, each imperfectly transmitting film comprising: Reducing the light intensity by a predetermined percentage in transmission through the completely transmissive film, the reticle substrate allowing substantially all of the incident light to pass; b) removing the imperfectly transmissive film deposited in step a) Overlying and applying an opaque film, said opaque film blocking light and substantially all incident light is attenuated; c) A first layer of a photoresist film having a pattern having a first opening penetrating the photoresist film is formed over the opaque film deposited in step b) to define a predetermined region of the opaque film. Exposing; d) etching the predetermined region of the opaque film exposed in the step c) to expose a predetermined region of the imperfectly permeable film; and e) exposing in the step d). Etching the predetermined area of the partially permeable film to expose a predetermined area of the reticle substrate; and f) forming a second opening through the photoresist film over the opaque film. Forming a second layer of photoresist film having a predetermined area of the opaque film, and g) etching the predetermined area of the opaque film exposed in step f). And ring, exposing a predetermined area of the incomplete permeable membrane, h)
Exposing a photosensitive photoresist substrate having a predetermined thickness to light transmitted through the reticle for a predetermined time, and exposing the photosensitive photoresist substrate through the predetermined area of the reticle substrate exposed in the step e). The transmitted light exposes a first photoresist area to a first dose, and the light transmitted through the predetermined area of the partially transparent film exposed in step g) is a second light. Exposing the photoresist area to a second dose and exposing the light transmitted through the remaining opaque film to a third photoresist area to a third dose; and i) the step h). Developing the exposed photoresist substrate at step 1 to thereby form a photoresist profile having an opening in the first photoresist area, the photoresist profile comprising: The substrate substantially has a photoresist thickness in the third photoresist region and an intermediate thickness between the predetermined thickness and zero in the second photoresist region; The light guided to the reticle formed by exposing a predetermined area of the reticle substrate and the imperfectly permeable membrane generates light of at least three intensities, and the photoresist substrate is provided with a multi-level reticle. Transforming the profile into a profile having at least two thicknesses and openings, substantially replicating the profile, thereby achieving the above objectives.

The patterning method of the present invention is a method of patterning a photosensitive photoresist film from a single exposure to a light source, the method comprising: a) one of the photoresists;
Exposing an area to light of a first intensity to form an opening through the photoresist film, wherein the light of the first intensity is not substantially attenuated in transmission from the light source; B) exposing a region of the photoresist to light of a second intensity to form a region of the photoresist having a first thickness, wherein the light of the second intensity comprises the light source C) exposing one area of the photoresist to light of a third intensity and having a second thickness greater than the first thickness; and c) exposing one area of the photoresist to light of a third intensity. Forming a
The third intensity of light is substantially blocked in transmission from the light source, thereby achieving the above object.

The method of forming a photoresist profile of the present invention is a method of forming a photoresist profile on a substrate, the method comprising: a) providing a photoresist layer having a predetermined thickness on the substrate. Steps and
b) guiding light to the photoresist through a reticle having a first transmission intensity to form a first exposure pattern;
Directing light through the reticle having a second transmission intensity to the photoresist to form a second exposure pattern; and c) developing the photoresist to form a region in the first exposure pattern. Removing a first thickness of the photoresist that is less than the predetermined thickness, and removing a second thickness of the photoresist in a region of the second exposure pattern, whereby the profile comprises: Including regions of the photoresist having a plurality of different thicknesses;
Which achieves the above object.

According to a preferred embodiment, the step b) includes guiding light to the photoresist through a reticle having a third transmission intensity to form a third exposure pattern in the photoresist. Step c), wherein said step c) removes a third thickness of said photoresist in the region of said third exposure pattern, whereby said profile of a photoresist having at least three different thicknesses Including the step of including the region.

According to a preferred embodiment, the step b) comprises exposing the photoresist to light having the first transmission intensity to form the first exposure pattern, Exposing the photoresist to light of the second transmission intensity greater than the second exposure pattern to form the second exposure pattern.

Further, according to a preferred embodiment, the second
Is partially overlapped with the first exposure pattern.

According to a preferred embodiment, the second
The light used for the exposure pattern has a larger photon dose per unit area than the light used for the first exposure pattern, and the step c) comprises developing the photoresist to form the second exposure pattern. Removing substantially the entire predetermined thickness of the photoresist in a region and removing the first thickness less than the predetermined thickness in a region of the first exposure pattern.

The operation will be described below.

It is advantageous to utilize the strength attenuation characteristics of the halftone film in the manufacture of a photoresist mask.

Using the intensity attenuation characteristics of the halftone film,
It is advantageous to produce a multilevel photoresist mask or photoresist pattern and to etch the IC substrate material to multiple depths.

Light intensity attenuation characteristics of a halftone film for manufacturing a photoresist mask having a plurality of thicknesses;
It is advantageous to combine sharp phase features with the halftone film to produce sharp features and reduce errors caused by diffraction.

Thus, a reticle is provided which defines the predetermined illuminated area on the photosensitive photoresist surface, through which the incident light passes. The reticle has a first transmission level film that generates a first intensity transmission light, a second transmission level film that generates a second intensity transmission light greater than the first intensity, and a second transmission level film that generates a first intensity transmission light. A third transmission level film for generating transmission light of a large third intensity.

The second transmission level film transmits more than about 10% and less than about 90% of the incident light, so that the attenuation characteristics of the second transmission level film when light is directed to the photosensitive surface. A characteristic substantially intermediate between the first transmission level film characteristic and the third transmission level film characteristic such that the reticle forms at least three distinct intensities in the irradiated area of the photoresist.

A method for forming a reticle for transmitting light on a reticle substrate using a photolithography method is also provided. The method includes depositing at least one film over the reticle substrate to transmit a portion of the incident light, wherein the partially transmissive film transmits light through the partially transmissive film. And the substrate passes substantially all light incident on the substrate. The method includes depositing an opaque film over the reticle substrate, wherein the opaque film blocks light such that substantially all incident light is attenuated. The method etches a previously deposited opaque film and a selective portion of the previously deposited partially permeable film, thereby exposing predetermined areas of the reticle substrate and the partially permeable film. As a result, the light guided to the reticle is transmitted to the reticle substrate, imperfectly permeable film,
And a predetermined area of the remaining opaque film, thereby producing at least three light intensities.

Further, a method is provided for forming a photoresist profile on a substrate. The method includes providing a photoresist layer having a predetermined thickness on a substrate, and directing light to the photoresist through a reticle having a first transmission intensity, thereby forming a first exposure pattern on the photoresist. And guiding light to the photoresist through a reticle having a second transmission intensity;
Thereby forming a second exposure pattern on the photoresist. The method also includes developing the photoresist, thereby removing the first thickness of the photoresist that is less than the predetermined thickness in the area of the first exposure pattern, and removing the photoresist in the area of the second exposure pattern. Removing the second thickness of photoresist, whereby the profile has regions of the photoresist having a plurality of different thicknesses.

[0061]

FIG. 1 is a partial cross-sectional view showing a reticle used to form three vias and the relative intensity of light transmitted through the reticle. Incident light 10 from a light source (not shown) is guided to a reticle 12.
The reticle 12 includes a reticle substrate 14 made of a material such as quartz. On the substrate 14, a phase shift film 16
And two regions are located. Two regions of opaque films 18 and 19 of chromium or the like are located on the phase shift films 16 and 17. The transmitted light 20 exits the reticle 12 and travels to a photoresist film (not shown). A graph 22 of relative light intensity is displayed. At positions where the incident light passes through the substrate 14, the transmitted light has substantially 100% intensity with respect to the incident light. In a region where the incident light is guided to the phase shift film 16 and the opaque film 18, the transmitted light is substantially zero. Diffraction of light passing through the first aperture 24 and the second aperture 26 is mitigated by the influence of light transmitted through the phase shift film 16. Without the phase shift film 16, diffraction by the apertures 24 and 26 would produce an in-phase optical interference effect, thereby forming a higher intensity profile 30 as shown by the dotted line in the graph 22. Similarly, when the phase resist film 17 is removed, a higher intensity created by the in-phase light interference effect from the apertures 26 and 32 is formed, as shown by the dotted line 34. Areas of higher and unintended strength, indicated by dashed lines 30 and 34, cause deformation of photoresist profile 36 formed from reticle 12. Due to the deformation of the photoresist 36 indicated by the dotted lines 38 and 40, the photoresist profile 3
In the IC substrate etched from step 6, unintended etching eventually occurs.

FIGS. 2-5 show the formation of a three-level reticle using the method of the present invention. FIG. 2 is a partial cross-sectional view of the three-level reticle in a state where the first photoresist pattern is located above. The reticle 50 includes a quartz substrate 52, an imperfectly permeable film 54, and an opaque film 56.
And the first photoresist pattern 58 located above
And The photoresist 58 is used for the reticle 5
It is patterned at an opening 59 for etching to zero.

FIG. 3 is a partial cross-sectional view of the three-level reticle 50 shown in FIG. 2 after the first etching step. The opening etched over the opaque film 56 and the partially permeable film 54 is
Expose 0. The opening is located below the opening 59 of the resist 58.

FIG. 4 shows the second photoresist pattern 6.
FIG. 4 is a partial cross-sectional view of the three-level reticle 50 shown in FIG. The second resist pattern 62 has an opening for exposing a predetermined region 63 of the opaque film 56.

FIG. 5 is a partial cross-sectional view of the three-level reticle 50 shown in FIG. 4 after the second etching step. The opening etched in the region 63 of the opaque film 56 exposes a predetermined surface region 64 of the imperfectly permeable film 54.

FIG. 5 shows a reticle 50 in which incident light passes through reticle 50 to define a predetermined illuminated area on the photosensitive photoresist surface. Reticle 50 is the first
A first transmitting film 56 for generating transmitted light having an intensity of
A second transmission level film 54 for generating light of a second intensity higher than the second intensity, and a third transmission level film 52 for generating light of a third intensity higher than the second intensity. I have. In a preferred embodiment of the present invention, the third transmission level film 52 is a substrate and the second transmission level film 54
Are located above the third transmission level film 52, and the first transmission level film 56 is located above the second transmission level film 54.

The first transmission level film 56 is made of chromium (C
r), an opaque film selected from the group consisting of chromium oxide (CrO) and iron oxide, whereby the first
It is one feature of the present invention that the transmission level film 56 substantially blocks incident light. Also, the third transmission level film 52 is selected from the group consisting of quartz, synthetic quartz, and glass, whereby the third transmission level film 52 is formed.
It is an aspect of the present invention that is transparent, so that substantially all incident light is transmitted. In a preferred embodiment of the present invention, the first transmission level film 56 has a first transmission level opening penetrating the first transmission level film 56 for exposing a predetermined region 64 of the second transmission level film 54. And the second transmission level region 64 is for exposing a predetermined region 60 of the third transmission level film 52,
It has a second transmission level opening penetrating through the second transmission level film 54. Typically, the thickness of each layer is 110 nanometers (nm) for the chrome opaque layer and 8 for the imperfectly permeable membrane.
0 nm, 0.09 inch for the quartz substrate.

The second transmission level film 54 delays the phase of the light by a predetermined amount, so that the phase difference between the transmission level films of the reticle improves the resolution of the transmitted light intensity. As a result, in-phase light interference effects at adjacent illuminated boundaries of the photoresist are reduced. One feature of the present invention is that the second transmission level film 54 delays the phase of the transmitted light by about 90 degrees.

FIG. 6 is a partial cross-sectional view of a two-level photoresist pattern formed from a three-level reticle. Prior to exposure through the reticle, the photoresist thickness is about 2 microns, between the illustrated 11.0 and 12.8 micron boundaries. After exposure through the reticle, the two-level resist pattern shown in FIG. 6 is developed. About 1 micron of the resist is removed, thereby forming an intermediate level having a thickness of about 0.5 microns. To reduce the size of the vias, phase shifting techniques known in the art are used to create a single level resist profile. FIG. 7 is a partial cross-sectional view of a two-level photoresist pattern formed from a three-level reticle using a phase shift to increase pattern resolution. The via is substantially smaller than the via of FIG. 6, and the intermediate surface surrounding the via is flatter. Thus, the reticle uses an imperfectly permeable film to create an intermediate intensity, thereby forming an intermediate resist level, and the reticle uses an imperfectly permeable film for phase shifting to control resolution. It has been found that the use of a 180 degree phase shift film results in excessive cancellation in the area of the resist surrounding the via. Optimum results are obtained when using cancellation of only a part of the diffracted light. A 30% transmission intensity (attenuating 70% of the incident light) using an imperfectly transmitting film with a 90 degree phase shift has been found to be effective.

In a preferred form of the invention, the second transmission level film 54, ie, the partially permeable film 54, is selected from the group consisting of indium tin oxide and molybdenum oxynitride silicide, thereby providing a second transmission level film. The film 54 attenuates the intensity of the transmitted light by a predetermined percentage.

In a preferred form of the invention, the second transmission level film 54 transmits more than about 10% and less than about 90% of the incident light, thereby providing the second transmission level film 54.
Has an attenuation characteristic substantially intermediate between the first transmission level film 56 and the third transmission level film 52. as a result,
When light is directed to the photosensitive surface, the reticle 50 creates at least three distinct intensities on the illuminated area of the photoresist.

It is one feature of the present invention that the incident light guided to the reticle 50 has a predetermined wavelength and a predetermined intensity. I-line light of 0.365 μm wavelength generated from a mercury arc lamp is typically used as an incident light source (not shown). Alternatively, a wavelength of 0.248
Various other wavelengths can be used, such as a μm krypton fluoride laser. The light intensity on the reticle is typically 5
00 to 1000 watts. The method of the present invention is not limited to a particular light wavelength band, but is applicable to all suitable wavelengths.

FIG. 8 is a graph showing the relationship between the resist thickness, the exposure time, and the transmission characteristics of the imperfectly permeable film. A normalized exposure of 1.0 corresponds to the exposure time required to completely remove the photoresist (after development). Typically, about 100 to completely expose the photoresist
Requires an exposure time of ~ 300 ms. The use of an imperfectly transmissive film (mask) with a transmission of 30% makes it possible to produce a resist thickness of about 10,000 angstroms using a normalized exposure of about 0.5. The intermediate level thickness in the photoresist can be adjusted by varying the dose to the resist, which is a function of light intensity and time. However, low doses (much less than 0.5 normalized exposure) do not provide enough light to consistently form vias through the resist profile. At high doses (much more than 0.5 normalized exposure), the via size is often too large and the via walls are often inclined. Thus, the resist is irradiated inaccurately to the area of the resist where the via is to be formed, thereby forming an intermediate level at the appropriate thickness in the profile without disadvantageous via formation by the profile. It is possible to select an irradiation time so as to perform light irradiation accurately by using a 30% transmittance film.

FIGS. 9 to 12A show a method of forming a multilevel reticle having a plurality of second transmission level films. FIG. 9 is a partial cross-sectional view of the multi-level reticle 70. The reticle 70 includes an opaque film, that is, a first transmission level film 72, a first partially permeable film 74, a second partially permeable film 76, and a transparent substrate, that is, a third transmission level film. A membrane 78 and overlying it;
First photoresist profile 80 with openings
And

FIG. 10 is a partial cross-sectional view of the multi-level reticle 70 of FIG. 9 after the first etching step.
The opening is etched across the opaque film 72, the second partially permeable film 76 and the first partially permeable film 74, thereby exposing a predetermined surface area 82 of the substrate 78. The etched opening is located below the opening in the pattern of the resist 80 shown in FIG.

FIG. 11 is a partial cross-sectional view of the multi-level reticle 70 shown in FIG. 10 with the second photoresist profile 84 positioned above. The resist profile 84 has an opening for exposing a predetermined surface area 86 of the opaque film 72.

FIG. 12A is a partial cross-sectional view of the multi-level reticle 70 shown in FIG. 11 after the second etching step. After the etching, the predetermined surface region 88 of the first partially permeable film 74 is exposed. Reticle 70
Incident on the opaque film 72 at the first transmission level. The incident light passes through the first imperfectly transmitting film 74 and the second
At the second intensity. Incident light transmits through the substrate 78 at a third intensity in the area of the exposed surface 82.

The reticle 70 shown in FIG. 9 to FIG.
Similar to the reticle 50 of FIGS. 2 to 5 except that a plurality of second transmission level films are provided. The plurality of second transmission level films 74 and 76 each generate transmitted light at one of a plurality of second intensities greater than the first intensity and less than the third intensity, thereby producing a first transmission light. A range of light of two intensities is provided. The present invention is the second
However, the present invention is not limited to the case where only two transmission level films are used, and more second transmission level films can be used. Alternatively, the reticle 70 includes a plurality of second transmission level films 74, 76.
And a reticle 50 having a first transmission level membrane consisting of A plurality of second transmission level membranes 74;
Reference numerals 76 and 72 denote imperfectly permeable membrane layers, respectively, so that the intensity characteristics of the light transmitted through the plurality of second level films 74, 76 and 72 accumulate, thereby accumulating the first transmitted level film. Light transmission characteristics are created.

That is, the second transmission level film is formed as shown in FIG.
Combined as shown in (a) to obtain the transmission attenuation and phase shift caused by the combination of two or more imperfectly permeable membranes. FIG. 12 (b)
FIG. 2 is a partial cross-sectional view of a multi-level reticle having a plurality of imperfectly permeable level membranes. A third photoresist pattern may be formed, thereby exposing a portion of the first transmission level film 74. Next, the first transmission level film 74 is etched, thereby exposing the region 89 of the second transmission level film 76. The light is then transmitted through the reticle at four intensities (and phases). That is, the light intensity of about 0% transmitted through the opaque film, the light intensity transmitted through the region 88 having the combination of the first partially transparent film 74 and the second partially transparent film 76, and the second Light intensity transmitted through a region 89 that is the transmission level film 76;
The intensity of light transmitted through the region 82 of the quartz substrate 78. This process can be repeated for additional layers of the partially permeable membrane.

The first permeation level membrane comprises a first number of the plurality of imperfectly permeable membrane layers 74, 76 and 72, ie, substantially all of the membranes, and the second permeation level membrane has a second permeation level. It is a feature of the present invention that the level membrane comprises a second number of the less than the first number of imperfectly permeable membrane layers 74, 76 and 72. In the present invention, the number of incompletely permeable membrane layers of the first transmission level membrane is not limited to only three, and more incompletely permeable membrane layers can be used.

FIG. 13 is a partial cross-sectional view of a three-level reticle that transmits incident light at three intensities on a photosensitive surface. The three-level reticle 90 includes a transparent substrate 92, an incompletely permeable film 94, and an opaque film 96. Light 98 incident on reticle 90 is transmitted light 1 having a plurality of intensities.
Output as 00. For simplicity, the lenses typically used between reticle 90 and photoresist mask 102 are not shown. Some exposure systems expose the photoresist to the same size as the reticle, but use a lens in the reduction system,
5 times or 1 times the reticle pattern
It is common to generate a pattern that is 0 times smaller on a resist. Light transmitted through the opaque film 96 is substantially blocked at the first region 104 of the photoresist 102 so as not to substantially affect the photoresist 102. Light transmitted through the imperfectly transmitting film 94 has a transmission intensity of 30% with respect to the incident light 98,
Thereby, the first level 10 is added to the photoresist 102.
6 are formed. The incident light 98 passing through the substrate 92 at the third intensity forms an opening 108 in the resist 102.

Alternatively, FIG. 13 can be described as a reticle 90 that transmits incident light 98 and thereby creates a profile pattern having a plurality of thicknesses 102. The reticle 90 includes a partially permeable film 94 that attenuates a predetermined percentage of incident light, thereby forming a photoresist region 106 having a first thickness. The reticle 90 is an opaque film 96
The opaque film 96 is provided with substantially all incident light 9.
8 and thereby a second greater than the first thickness
A photoresist region 104 having a thickness of The reticle 90 includes a transparent substrate 92 that transmits substantially all incident light, thereby forming a photoresist region 108 having a third thickness less than the first thickness. In a preferred form of the invention, the third thickness is substantially zero so that an opening is formed in photoresist film 102.

In still another description, reticle 90
Transmits incident light 98, thereby forming a profile pattern having a plurality of thicknesses on the photosensitive photoresist film 102. The reticle 90 has a transparent substrate 92 that allows substantially all of the incident light 98 to pass through, thereby forming an opening 108 in the photoresist film 102. The reticle 90 includes substantially all incident light 98
Also has an opaque film 96, which blocks the photoresist, thereby forming a photoresist region having a second thickness. The reticle 90 includes a partially transparent film 94 that attenuates a predetermined percentage of incident light 98, thereby forming a photoresist region 106 having a first thickness. The first thickness is about one third of the second thickness.

FIG. 14 shows steps of a method for forming a three-level reticle of the present invention. The reticle transmits incident light. The transmitted light illuminates a plurality of regions of the photosensitive surface, each region being illuminated with a predetermined level of transmitted light,
This is one feature of the present invention. In step 120, a reticle substrate is provided. In step 122, at least one film for transmitting a part of incident light is deposited on the reticle substrate. The partially permeable film reduces the light intensity by a predetermined percentage in transmission through the partially permeable film, and the substrate allows substantially all light incident on the substrate to pass. In step 124, an opaque film is deposited over the reticle substrate. The opaque film blocks light so that substantially all incident light is attenuated. In step 126, the opaque film deposited in step 124 and a selective portion of the partially permeable film deposited in step 122 are etched, thereby exposing predetermined areas of the reticle substrate and the partially permeable film. . In step 128, a product, a reticle that transmits light through predetermined regions of the reticle substrate, the partially permeable film and the remaining opaque film, thereby producing three intensities of light, is obtained. The transmitted light having three intensities produces a patterned profile having at least two thicknesses at the photosensitive surface;
It is one feature of the present invention that an opening is typically obtained through the surface.

Step 122 deposits a plurality of imperfectly permeable films such that the light transmission characteristics of each imperfectly permeable film are accumulated, thereby gradually attenuating the incident light passing through the imperfectly permeable film. It is one feature of the present invention to include forming in a continuous layer. In this step, the plurality of partially permeable films each have a different etch selectivity, and etching of adjacent partially permeable films requires a separate etching process. Step 1
26 exposes an underlying imperfectly permeable membrane layer by etching selective portions of the predetermined imperfectly permeable membrane, such that a combination of a plurality of imperfectly permeable membranes is capable of transmitting a plurality of transmitted light. Providing strength is also a feature of the present invention.

The following is one feature of the present invention. Step 122 involves depositing the plurality of partially permeable membranes such that the plurality of partially permeable membranes that substantially duplicate the light transmission properties of the opaque membrane provide cumulative attenuation.
As a result, step 124 includes step 122 because the transmission of light is substantially blocked by the deposition of the plurality of partially permeable membranes.

In a preferred embodiment of the present invention, step 122 includes depositing a partially permeable membrane to form a layer adjacent to and located on the reticle substrate, and step 124. Involves depositing an opaque membrane to form a layer adjacent to and overlying the partially permeable membrane. Step 1
26 includes etching selected areas of the opaque film to direct light to the partially permeable film without transmitting light through the opaque film. Step 126 includes selecting the partially permeable and opaque films such that light is introduced into selected areas of the reticle substrate without transmitting light to either the opaque or partially permeable films. Etching a portion, whereby at least 3
Light having two intensities illuminates the photosensitive surface.

In a preferred form of the invention, step 126 includes forming a first layer of photoresist having a first pattern. The first layer is overlying the opaque film and has an opening therethrough. Step 126 also includes exposing the openings in the previously formed photoresist pattern.
Etching a predetermined region of the opaque film, thereby exposing a first region of the partially permeable film underlying the opaque film, and etching a first region of the partially permeable film, Exposing a predetermined area of the reticle substrate located below the partially permeable membrane. Further, step 126 includes forming a second layer of photoresist. A second layer is located over the opaque film and has an opening through the second layer.
Having the following pattern. Finally, a step 126 etches a predetermined area of the opaque film exposed through the opening in the second pattern in the overlying photoresist, thereby forming an underlying layer of the opaque film. Exposing a second region of the fully permeable film, whereby light introduced into a predetermined region of the reticle substrate is transmitted at a first intensity and the second region of the imperfectly permeable film and the underlying substrate. The light introduced into the region is transmitted at a second intensity and the light introduced into the remaining opaque film is transmitted at a third intensity through the opaque film, the underlying imperfectly permeable film and the substrate, and Illuminating the resulting photosensitive surface.

FIG. 15 shows steps of a method for forming a multilevel photoresist pattern according to the present invention. Step 1
At 40, a reticle substrate is provided. Step 14
At 2, one or more films are deposited over the reticle substrate, thereby transmitting some of the incident light. Each partially permeable membrane reduces the light intensity by a predetermined percentage in transmission through the partially permeable membrane, and the reticle substrate allows substantially all incident light to pass. In step 144, an opaque film is deposited over the partially permeable film deposited in step 142. The opaque film blocks light so that substantially all incident light is attenuated.
In step 146, a first layer of photoresist film is formed over the opaque film deposited in step 144 and having a pattern including a first opening through the photoresist film, thereby forming a first layer of opaque film. A predetermined area is exposed. In step 148, a predetermined area of the opaque film exposed in step 146 is etched, thereby exposing a predetermined area of the partially permeable film.

In step 150, a predetermined area of the partially permeable film is etched in step 148, thereby exposing a predetermined area of the reticle substrate. In step 152, a second layer of photoresist film having a second opening through the photoresist film is formed over the opaque film, thereby exposing a predetermined region of the opaque film. In step 154, a predetermined area of the opaque film exposed in step 152 is etched, thereby exposing a predetermined area of the partially permeable film. In step 156, a predetermined thickness of the photosensitive photoresist substrate is exposed to light transmitted through the reticle for a predetermined time. At this time, the light transmitted through the predetermined area of the reticle substrate exposed in step 150 is transmitted through the first photoresist area to the first photoresist area.
The light passing through the predetermined area of the partially permeable film exposed at step 154 is exposed to the second photoresist area to the second dose, and the light transmitted through the remaining opaque film is Exposing a third photoresist area to a third dose. As described in the discussion of FIG. 8, the dose is a function of the intensity of the transmitted light on the surface and the time the surface was exposed.

In step 158, the photoresist substrate exposed in step 156 is developed, thereby forming a photoresist profile having an opening in the first photoresist region. The photoresist profile has a photoresist thickness substantially in the third photoresist region and an intermediate thickness between the predetermined thickness and zero in the second photoresist region. Thereby, light introduced into the reticle formed by exposing predetermined areas of the reticle substrate and the partially permeable film generates light of at least three intensities. In step 160, the product,
A photoresist substrate is obtained that has been transformed into a profile having at least two thicknesses and openings that substantially replicates the profile of the multi-level reticle.

FIG. 16 illustrates the steps of the method of the present invention for patterning a photoresist film having multiple thicknesses from a single exposure. In step 170, a photosensitive photoresist film is provided from a single exposure to a light source. In step 172, one region of the photoresist is exposed to light of a first intensity, thereby forming an opening in the photoresist film. The first intensity of light is not substantially attenuated in transmission from the light source. In step 174, the photoresist is exposed to light of a second intensity, thereby forming a photoresist region having a first thickness. The second intensity of light is partially attenuated in transmission from the light source. At step 176, the areas of the photoresist are exposed to light of a third intensity, thereby forming areas of the photoresist having a second thickness greater than the first thickness. The third intensity of light is substantially blocked in transmission from the light source. In step 178, a product, ie, a photoresist film having a plurality of thicknesses, is obtained.

FIG. 17 illustrates a method of the present invention for forming a photoresist profile having two exposure patterns from a single reticle. In step 180, a substrate for a photoresist profile is provided. In step 182, a layer of photoresist having a predetermined thickness is provided on the substrate. In step 184, the first
Light is guided to the photoresist through a reticle having a transmission intensity of, thereby forming a first exposure pattern, and light is guided to the photoresist through the reticle having a second transmission intensity, whereby A second exposure pattern is formed. In step 186, the photoresist is developed, thereby removing a first thickness of the photoresist less than a predetermined thickness in the area of the first exposure pattern, and removing a second thickness of the photoresist in the area of the second exposure pattern. Remove thickness. In step 188, a profile is obtained that includes regions of the product, i.e., a plurality of photoresists having different thicknesses.

The following is one feature of the present invention. Step 184 includes directing light through a reticle having a third transmission intensity to the photoresist, thereby forming a third exposure pattern in the photoresist, and step 186 includes forming a third exposure pattern. Removing the third thickness of the photoresist in the region, whereby the profile includes regions of the photoresist having at least three different thicknesses.

In a preferred embodiment, step 1
84, exposing the photoresist at a first transmission intensity, thereby forming a first exposure pattern, and exposing the photoresist at a second transmission intensity greater than the first transmission intensity; Forming a second exposure pattern. In a preferred embodiment, the second exposure pattern at least partially overlaps the first exposure pattern. In many exemplary applications, photoresist is used to form vias having connection lines located thereon. The via is formed by a hole formed in the resist, that is, by the second exposure pattern. The line is at the intermediate level of the resist, ie, the first
At the level of the exposure pattern. In order to make the vias and lines electrically communicate, the exposure patterns must overlap.

The following notes are supplemented in the description of FIG. The light used for the second exposure pattern has a larger photon dose per unit area than the light used for the first exposure pattern. Also, step 186 develops the photoresist, thereby substantially removing all of the predetermined thickness of the photoresist in the region of the second exposure pattern;
And removing only the first thickness less than the predetermined thickness in the region of the first exposure pattern. As described in FIG. 8, the photoresist is removed by a dose calculation. Dose is a measurement that depends on light intensity and time over a given area. The same calculation can be performed using photons per unit area.

Although the reticle and resist profile have been described with a primary focus on forming a two-level resist profile from a three-level reticle, the invention is not so limited. The method described in detail above
It has more than three levels, thereby being applicable to reticles for forming more than two levels of resist profiles.

FIGS. 18 (a) to 18 (d) illustrate a method of forming a multi-level reticle from a multi-level photoresist profile according to another embodiment of the present invention. In FIG. 18A, a photoresist film 190 includes an opaque layer, ie, a chromium layer 192, and an incompletely transparent film, ie, a halftone (HT) film 194.
And a multi-level reticle 191 having a quartz substrate 196. In FIG. 18B, the resist is removed to two levels using an electron beam (e-beam). The e-beam removes the resist down to the intermediate layer 198 and completely removes the resist at other locations, thereby exposing the region 200 of the opaque film 192. 18C, reticle 191 is etched such that opaque film 192 and partially permeable film 194 under region 200 are removed, thereby exposing region 202 of substrate 196. In FIG. 18D, the region 204 of the opaque film 192 is exposed.
A part of the resist 190 is removed. In FIG. 18E, the region 204 of the opaque film 192 is etched,
The region 206 of the partially permeable membrane 194 is exposed. FIG.
8 (e), the remaining resist 190 is removed. Reticle 191 in FIG. 18E is the same as reticle 50 in FIG. However, reticle 191
It is formed by one resist development process. Also,
The alignment characteristics are better than those possible with the reticle of FIG. As shown in FIG. 4, the region 200 (60 in FIG. 4) requires alignment accuracy with the second resist pattern.
An alignment accuracy of 0.005 microns between 6 and region 200 is achieved. Region 206 typically corresponds to a line (trench) interconnect in the intermediate interlevel of the dielectric, and region 200 corresponds to a via. Although the above process describes the formation of a three-level reticle, the invention is not so limited. The same process can be applied to form a resist having three or more levels over reticle 191 and thereby form a reticle having four or more levels. Modifications and changes within the scope of the present invention are made by those skilled in the art.

[0099]

In accordance with the present invention, there is provided a reticle through which incident light passes, thereby defining a predetermined illuminated area on the photosensitive photoresist surface. A reticle has a first transmission level film for generating a first intensity of transmitted light, a second transmission level film for generating a second intensity of the transmitted light greater than the first intensity, and a reticle having a second intensity greater than the first intensity. And a third transmission level film for generating transmission light having a large third intensity, so that a single exposure can form a multilevel resist having a plurality of thicknesses.

According to the present invention, a plurality of thicknesses can be formed on a multilevel resist by a single exposure through a multilevel reticle, so that misalignment between levels in a multilevel resist can be suppressed.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a reticle for forming three vias and the relative intensity of light transmitted through the reticle (prior art).

FIG. 2 is a partial cross-sectional view of a three-level reticle with a first photoresist pattern positioned above;

FIG. 3 is a partial cross-sectional view of the three-level reticle of FIG. 2 after a first etching step.

FIG. 4 is a partial cross-sectional view of the three-level reticle of FIG. 3 with a second photoresist pattern positioned above;

FIG. 5 is a partial cross-sectional view of the three-level reticle of FIG. 4 after a second etching step.

FIG. 6 is a partial cross-sectional view of a two-level photoresist pattern formed from a three-level reticle.

FIG. 7 is a partial cross-sectional view of a two-level photoresist pattern formed from a three-level reticle using a phase shift to increase pattern resolution.

FIG. 8 is a graph showing the relationship between resist thickness, exposure time and transmission characteristics of a partially permeable film.

FIG. 9 is a partial cross-sectional view of a multi-level reticle.

FIG. 10 is a partial cross-sectional view of the multi-level reticle of FIG. 9 after a first etching step.

FIG. 11 is a partial cross-sectional view of the multi-level reticle of FIG. 10 with a second photoresist pattern positioned above;

FIG. 12 (a) is a partial cross-sectional view of the multi-level reticle of FIG. 11 after a second etching step. Sectional view, (b) is a partial cross section of a reticle having a plurality of imperfectly permeable level membranes.

FIG. 13 is a partial cross-sectional view of a three-level reticle that transmits incident light to a photosensitive surface at three intensities.

FIG. 14 illustrates steps in a method of the present invention for forming a three-level reticle.

FIG. 15 illustrates steps of a method of the present invention for forming a multi-level photoresist pattern.

FIG. 16 illustrates steps of a method of the present invention for patterning a photoresist film having multiple thicknesses from a single exposure.

FIG. 17 illustrates a method of the present invention for forming a photoresist profile having two exposure patterns from a single reticle.

FIGS. 18 (a)-(e) illustrate a method of forming a multi-level reticle from a multi-level photoresist profile, illustrating another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 50 3-level reticle 52 Quartz substrate (third transmission level film) 54 Incompletely permeable film (second transmission level film) 56 Opaque film (first transmission level film) 60 Predetermined area of quartz substrate 64 Incomplete transmission Surface area of conductive film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Dave Russell Evans United States Oregon 97007, Beaverton, Esb. 179 T.H. ) Inventor Bruce Dale Warwick USA 95005, Oregon, Beaverton, Essex Barlow Court 14095

Claims (34)

[Claims] 1. A reticle through which incident light passes to define a predetermined illuminated area on a photosensitive photoresist surface, the reticle producing a first intensity of transmitted light; A second transmission level film that generates a transmission light of a second intensity greater than the first intensity; and a third transmission level film that generates a transmission light of a third intensity greater than the second intensity. Reticle with 2. The third transmission level film is a substrate,
The reticle of claim 1, wherein the second transmission level film is located on the third transmission level substrate and the first transmission level film is located on the second transmission level film. 3. The method according to claim 1, wherein the first transmission level film is made of Cr, Cr.
The reticle of claim 1, wherein the reticle is an opaque film selected from the group consisting of O and iron oxide, whereby the first transmission level film substantially blocks incident light. 4. The third transmission level film is selected from the group consisting of quartz, synthetic quartz and glass, such that the third transmission level film is transparent so as to pass substantially all incident light. The reticle according to claim 1, wherein 5. The first transmission level film has a first transmission level opening penetrating the first transmission level film so as to expose a predetermined region of the second transmission level film,
The second transmission level region according to claim 1, wherein the second transmission level region has a second transmission level opening penetrating the second transmission level film so as to expose a predetermined region of the third transmission level film. Reticle. 6. The reticle transmission such that the second transmission level film retards the phase of light by a predetermined amount, thereby reducing in-phase light interference effects at adjacent illuminated boundaries of the photoresist. The reticle of claim 1, wherein the phase difference between the level films improves the resolution of transmitted light intensity. 7. The reticle of claim 6, wherein the second transmission level film delays the phase of the transmitted light by about 90 °. 8. A plurality of second transmission level membranes are provided,
Each of the plurality of second transmission level films generates transmitted light at one of a plurality of second intensities greater than the first intensity and less than the third intensity, thereby: The light of a second intensity range is provided.
Reticle described in. 9. The first permeation level membrane comprises a plurality of second permeation level membranes, each of the plurality of second permeation level membranes being an imperfectly permeable membrane layer, The reticle of claim 1, wherein the intensity characteristics of light transmitted through the plurality of second transmission level films are cumulative such that light transmission characteristics of the transmission level film occur. 10. The first transmission level membrane includes a first number of the partially permeable membrane layers that is substantially all of the plurality of partially permeable membrane layers, and wherein the second transmission level membrane includes a first number of the partially permeable membrane layers. The level membrane is
The reticle of claim 9, comprising a second number of the partially permeable membrane layers less than the first number. 11. The second transmission level film is selected from the group consisting of indium tin oxide and molybdenum oxynitride, whereby the second transmission level film attenuates the transmitted light intensity by a predetermined percentage. Item 2. A reticle according to Item 1. 12. The second transmission level film transmits at least about 10% to less than about 90% of the incident light, whereby the attenuation characteristic of the second transmission level film is the first transmission level film. The reticle forms at least three distinct intensities on the illuminated area of the photoresist when light is directed to the photosensitive surface, being approximately halfway between the attenuation characteristic and the third transmission level film attenuation characteristic. A reticle according to claim 1. 13. A method of using photolithography to form a reticle transmitting incident light on a reticle substrate, comprising: a) at least one incomplete transmission covering the reticle substrate and partially transmitting the incident light. Depositing a permeable membrane, wherein the partially permeable membrane reduces light intensity by a predetermined percentage in transmission through the partially permeable membrane;
The reticle substrate passing substantially all light incident on the reticle substrate; and b) depositing an opaque film over the reticle substrate, wherein the opaque film blocks light. Wherein substantially all incident light is attenuated, and c) selective portions of the opaque film deposited in step b) and the partially permeable film deposited in step a) Is etched to expose predetermined regions of the reticle substrate and the partially permeable film, whereby light guided to the reticle is exposed to the predetermined regions of the reticle substrate, the partially permeable film and the remaining opaque film. Generating at least three light intensities transmitted through the photolithography. 14. A method of using photolithography to form a reticle on an reticle substrate for transmitting incident light, said transmitted light illuminating regions of a photosensitive surface, each of said regions having a predetermined level of transmitted light. Wherein the method comprises the steps of: a) depositing at least one partially permeable membrane over the reticle substrate, the partially permeable membrane partially transmitting incident light; Reducing the light intensity by a predetermined percentage in transmission through the imperfectly permeable membrane;
Said reticle substrate transmitting substantially all light incident on said reticle substrate; and b) depositing an opaque film over said reticle substrate, said opaque film blocking light. Wherein substantially all incident light is attenuated, and c) selective portions of the opaque film deposited in step b) and the partially permeable film deposited in step a) Is etched to expose predetermined regions of the reticle substrate and the imperfectly permeable film, whereby light guided to the reticle is exposed to the reticle substrate, the partially imperfectly permeable film and the remaining opaque film. Generating a patterned profile having at least two thicknesses on the photosensitive surface transmitted through the region. 15. The step a) includes depositing a plurality of imperfectly permeable membranes on successive layers, wherein the light transmission properties of each of the imperfectly permeable membranes are cumulative and the imperfectly transmitted Progressively attenuating the incident light passing through the transparent membrane, the plurality of imperfectly permeable membranes have different etching selectivities,
The etching of the adjacent partially permeable film requires a different etching process, and the step c) comprises etching a selective portion of the predetermined partially permeable film to form an underlying partially permeable film. 15. The method of using photolithography according to claim 14, wherein exposing a film layer, whereby the combination of a plurality of the partially permeable films provides a plurality of transmitted light intensities. 16. The method of claim 14, wherein the opaque film is selected from the group consisting of Cr, CrO, and iron oxide. 17. The method of claim 14, wherein the partially permeable film is selected from the group consisting of indium tin oxide and molybdenum oxynitride. 18. The method according to claim 14, wherein the reticle substrate is selected from the group consisting of quartz, synthetic quartz, and glass. 19. The imperfectly permeable film is capable of transmitting about one part of incident light.
15. The optical transmission system of claim 1, wherein 0% to less than about 90% of the incident light is transmitted, whereby the imperfectly transmissive film attenuation characteristic is substantially intermediate between the reticle substrate attenuation characteristic and the opaque film attenuation characteristic. 3. The method of using photolithography according to claim 1. 20. The step a) of depositing a plurality of partially permeable membranes such that the cumulative attenuation of the plurality of partially permeable membranes substantially duplicates the light transmission properties of the opaque membrane. 15. The method of claim 14, wherein step b) includes step a) because the plurality of partially transmissive films substantially block transmission of light. 21. The incompletely transmissive film retards the phase of incident light by a predetermined amount so that a phase difference introduced in transmission through the incompletely transmissive film improves the resolution of transmitted light intensity and improves photosensitivity. 15. The method of using photolithography according to claim 14, which reduces in-phase light interference effects in illuminating a conductive surface. 22. The step a) includes attaching the imperfectly permeable membrane to a layer adjacent to the reticle substrate and overlying the reticle substrate,
The step b) includes attaching the opaque film to a layer adjacent to and overlying the partially permeable membrane, and the step c) includes attaching the opaque film to the layer. Etching a selected portion of the opaque film such that light is introduced into the partially permeable film without transmitting light through the film, wherein step c) comprises:
A selected portion of the partially permeable film and the opaque film such that light is directed to a selected portion of the reticle substrate without transmitting light through either the opaque film or the partially permeable film. 15. The method of using photolithography according to claim 14, comprising etching the photosensitive surface by light having at least three intensities. 23. The step c) comprising: i) forming, over the opaque film, a first layer of a photoresist having a first pattern including an opening through the first layer. Ii) etching a predetermined area of the opaque film exposed through the opening provided in the pattern of the photoresist formed in the step i), thereby forming the non-conductive film located under the opaque film; Exposing a first region of the fully permeable membrane;
Etching the first region of the partially permeable membrane to expose a predetermined area of the reticle substrate located below the partially permeable membrane; iii) Forming the second layer of photoresist having a second pattern having openings through the two layers; and iv) the second pattern of the photoresist formed in step iii). Etching a predetermined region of the opaque film exposed through the opening therein to expose a second region of the imperfectly permeable film, thereby being introduced into the predetermined region of the reticle substrate Light is transmitted at a first intensity, and light introduced into the second region of the imperfectly permeable film is transmitted at a second intensity through the imperfectly permeable film and the underlying substrate; The light introduced into the remaining opaque film is not opaque. Film, the the incomplete permeable membrane and said substrate located thereunder is transmitted through the third strength, the photosensitive surface is illuminated, the method utilizing photolithography as claimed in claim 22. 24. The incident light guided to the reticle has a predetermined wavelength and a predetermined intensity.
3. The method of using photolithography according to claim 1. 25. A reticle for transmitting incident light to form a profile pattern having a plurality of thicknesses on a photosensitive surface, wherein the reticle attenuates a predetermined percentage of the incident light and has a first thickness. An incompletely permeable film forming a resist region; an opaque film blocking substantially all incident light to form a photoresist region having a second thickness greater than the first thickness; A transparent substrate that allows all incident light to pass through to form a photoresist region having a third thickness that is less than the first thickness. 26. The reticle of claim 25, wherein an opening having the third thickness substantially zero is formed in the photoresist film. 27. A reticle for transmitting incident light to form a profile pattern having a plurality of thicknesses on a photosensitive photoresist surface, said reticle transmitting substantially all incident light to form a reticle. A transparent substrate that forms an opening in the photoresist film, and an opaque film that blocks substantially all incident light to form a photoresist region having a second thickness; An imperfectly transmissive film that attenuates a percentage of the incident light, thereby forming a photoresist region having a first thickness, wherein the first thickness is about one third of the second thickness. Is a reticle. 28. A method for forming a photoresist pattern having a predetermined profile formed by exposing a predetermined pattern of light transmitted through a reticle formed over a reticle substrate, the method comprising forming a photoresist pattern. A) depositing at least one film that imperfectly transmits incident light over the reticle substrate, wherein each imperfectly transmitting film transmits light through the imperfectly transmitting film. Reducing the intensity by a predetermined percentage and allowing the reticle substrate to pass substantially all of the incident light; and b) depositing an opaque film over the imperfectly permeable film deposited in step a). Wherein the opaque film blocks light and substantially all incident light is attenuated; c) deposits in step b) Forming a first layer of a photoresist film having a pattern having a first opening penetrating the photoresist film, covering the opaque film thus formed, and exposing a predetermined region of the opaque film; d) etching the predetermined area of the opaque film exposed in the step c) to expose a predetermined area of the imperfectly permeable film; and e) the imperfect transmission exposed in the step d). Etching the predetermined region of the conductive film to expose a predetermined region of the reticle substrate; and f) forming a photoresist film covering the opaque film and having a second opening through the photoresist film. Forming a second layer to expose a predetermined area of the opaque film; and g) etching the predetermined area of the opaque film exposed in the step f) to remove the incomplete transparent film. Exposing a predetermined area of the transient film; and h) a photosensitive photoresist substrate having a predetermined thickness;
Exposing to light transmitted through the reticle for a predetermined time, wherein the light transmitted through the predetermined area of the reticle substrate exposed in step e) is a first light.
Exposing the photoresist area to a first dose, and light transmitted through the predetermined area of the partially permeable film exposed in step g) passes the second photoresist area to the second Exposing a dose and transmitting light through the remaining opaque film to expose a third photoresist area to a third dose; i) the photoresist substrate exposed in step h) Developing a photoresist profile having an opening in the first photoresist region, wherein the photoresist profile substantially reduces a predetermined thickness of the photoresist in the third photoresist region. And having an intermediate thickness between the predetermined thickness and zero in the second photoresist region, thereby providing a location at the reticle substrate and the partially permeable membrane. Light directed at the reticle formed by exposing a constant region produces at least three intensities of light and transforms the photoresist substrate into at least two thicknesses that substantially replicate the profile of a multilevel reticle. Deforming into a profile having a height and an opening;
A method of forming a photoresist pattern, comprising: 29. A method of patterning a photosensitive photoresist film from a single exposure to a light source, comprising: a) exposing one region of the photoresist to light of a first intensity; Forming an opening through the photoresist film, wherein the light of the first intensity is not substantially attenuated in transmission from the light source; and b) forming one region of the photoresist in the first region. Exposing a photoresist region having a first thickness to light of a second intensity, the second intensity of light being partially attenuated in transmission from the light source; C) exposing an area of the photoresist to light of a third intensity to form a photoresist area having a second thickness greater than the first thickness; The light of the intensity Substantially blocking in their transmission. 30. A method of forming a photoresist profile on a substrate, the method comprising: a) providing a photoresist layer having a predetermined thickness on the substrate; b) Guiding light to the photoresist through a reticle having a first transmission intensity to form a first exposure pattern;
Directing light through the reticle having a second transmission intensity to the photoresist to form a second exposure pattern; c) developing the photoresist and in the area of the first exposure pattern, Removing a first thickness of the photoresist less than the predetermined thickness and removing a second thickness of the photoresist in a region of the second exposure pattern, such that the profile comprises a plurality of Including regions of photoresist having different thicknesses of
A method of forming a photoresist profile. 31. The step b) includes guiding light to the photoresist via a reticle having a third transmission intensity to form a third exposure pattern in the photoresist. c) removing a third thickness of the photoresist in the regions of the third exposure pattern, whereby the profile includes regions of the photoresist having at least three different thicknesses. 31. The method of forming a photoresist profile according to claim 30. 32. The step b) comprises exposing the photoresist to light of the first transmission intensity to form the first exposure pattern, wherein the second exposure intensity is greater than the first transmission intensity. 31. The method of forming a photoresist profile according to claim 30, comprising exposing the photoresist to light having a transmission intensity to form the second exposure pattern. 33. The second exposure pattern, at least a part of which overlaps the first exposure pattern.
0. A method for forming a photoresist profile according to item 0. 34. The light used for the second exposure pattern has a larger photon dose per unit area than the light used for the first exposure pattern, and the step c).
Develops the photoresist to substantially remove the entire predetermined thickness of the photoresist in the region of the second exposure pattern, and in the region of the first exposure pattern, 31. The method of forming a photoresist profile according to claim 30, comprising removing the small first thickness.